Prior art illumination systems range widely in their basic design depending on such factors as the desired use of the generated image, the general size and reflectivity of the object to be illuminated, and the specific features of the object sought to be captured. Such features include measurement of relative position, detection of specific shapes for analysis, and the detection of flaws or other imperfections. In order to capture and analyze such features, images of the object, or surfaces thereof, as well as images of the shadows cast by the objects are advantageously used by state of the art inspection systems. In prior art illumination systems employing annular light sources, which tend to provide a cone of light, the light is scattered and tends to illuminate surfaces which are not of interest for the inspection process. Other prior art illumination systems employing light sources whose rays converge upon the object being imaged also diminish the information obtainable by an attached inspection system because such converging light rays tend to distort or eliminate useful shadow images.
Moreover, known illumination systems typically employ machined blocks or other significantly complex and expensive to produce means for mounting conventional light sources (e.g., conventional mounted light emitting diodes). The cost involved in machining the mounting means, inserting the conventional light sources, the accompanying wiring and circuit lay-out and overall assembly time adds to the complexity and cost of such known illumination systems. A problem related to the above-mentioned conventional manufacturing problems is the insufficient light intensity produced by known illumination systems. Specifically, conventional light emitting diodes have a predetermined minimum mounting separation distance as employed in the prior art systems thus limiting diode placement density. It has been found that the relatively low diode density generates insufficient light intensity to provide adequate illumination for certain imaging and inspection applications.
Another problem in the prior art is the lack of flexibility in changing lighting patterns for different imaging applications.
Thus, there is a need for an improved illumination system for generating an image of an object that overcomes or minimizes the above-mentioned problems.